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The super thermal conductive mandrel technology recently developed by Acrolab Ltd. makes it possible to cure filament-wound pipe and tube sections without the need for cure ovens. The mandrel is heated uniformly, while rotating, by an induction heating system.
Trademarked the “Isomandrel”, the new mandrel design consists of an internal process within the mandrel which enhances its thermal conductivity and thermal reactivity. The process permits heat to be applied in a localized concentration that is then rapidly and homogeneously redistributed over the complete mandrel working surface.
An innovative design
When the Isomandrel technology is coupled with induction heating, the mandrel and filament winding system continue rotating while being heated to an optimum controlled temperature to achieve cure. This heating can occur while the assembly is still rotating in the winding machine or on a rotating fixture within the manufacturing cell.
Acrolab Ltd., working as a technology team with McClean Anderson and Ameritherm, constructed the curing cell at McClean Anderson’s laboratory. The induction-heated Isomandrel curing station was used to cure a number of 1.20-m-long pipe sections wound with glass and carbon fibre epoxy prepregs, provided by TCR Composites of Ogden, Utah, and wound on a 76-mm outer diameter Isomandrel.
At the end of the winding cycle, the sections were successfully cured on the new mandrel design using an EKOHEAT induction power supply and coil assembly while the Isomandrel and winding were still mounted and rotating at a reduced 10 rpm on the Super Hornet Winder.
By providing high thermal energy uniformly over the entire mandrel surface outward and through the filament winding, the cure is completed in a much shorter time with less energy while providing a significantly more uniform cure and resin-rich inner diameter.
Ameritherm and McClean Anderson are currently developing a fully software/hardware integrated station to provide the controlled power and recipe requirements to integrate with Acrolab’s Isomandrel technology.The combination of Isomandrel’s capability to provide high speed of response and near isothermal conditions on the complete working surface of the mandrel, coupled with the three-term process temperature control and the high-speed-of-response induction heating capability of the Ameritherm power supply, results in optimum “ramp, soak and hold” process control at the most advantageous curing temperatures.